1. Field of the Invention
The automotive industry is increasingly focusing on reducing parasitic losses in power transmission systems to improve fuel economy. One way to achieve such a reduction is to transform each system powered by an engine belt so that it can be turned on and off as needed. This is often accomplished by multiple bearings and clutches. For example, in a water pump application, having an “off” setting is beneficial during initial operation of an engine to permit heating of the engine to a steady operational temperature more quickly so that the engine burns fuel more efficiently.
Packaging, thermal expansion, and assembly stack-up tolerances create issues for the design and manufacture of a clutched system in various applications. These issues are addressed by the present invention.
2. Description of Related Art
Bearings involved in clutched water pumps, which involve relatively new technology, are similar to bearings used in compressors, which involve mature technology. Typically, one bearing, or a set of bearings, is used to support a shaft that rotates an impeller blade in a water pump, while another bearing, or another set of bearings, is used to allow an engine pulley to rotate. A clutch system connects the shaft to the pulley, allowing them to rotate together. When the clutch is disengaged, the pulley bearing rotates along with the engine, but the shaft bearing of the water pump does not rotate.
Current bearing assemblies typically require multiple layers to work perfectly with each other for ideal function. The layers typically required for a clutched water pump include a pulley bearing outer ring, a rolling element layer, a pulley bearing inner ring, an aluminum pump housing, a shaft bearing outer ring, another rolling element layer, and a shaft. For other applications, there may also be a bearing inner ring between the innermost rolling elements and the shaft.